Thermal engine exhaust reactor with over-temperature protection

ABSTRACT

A thermal reactor preferably having in a preferred embodiment, an insulated reaction chamber in which engine exhaust gases are exothermically reacted to reduce undesirable exhaust emissions. The inner liner of the reaction chamber is protected against overheating during temporary periods of excessive temperature operation by surrounding the outer surfaces of the liner with a fusible material having a melting point between the normal operating temperature of the reactor and the maximum operating temperature. The latent heat of fusion of the fusible material acts as a heat sink, absorbing heat upon melting of the material so as to maintain the walls of the inner liner below their maximum operating temperatures during temporary periods of abnormally high temperature operation due to engine malfunction or the like.

United States Patent [191 'Mattavi THERMAL ENGINE EXHAUST REACTOR WITHOVER-TEMPERATURE PROTECTION [75] Inventor: James N. Mattnvl, Mt.Clemens,

Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Dec. 27, 1971 211 Appl. No.: 211,972

[52] US. Cl. 60/298, 23/277 C, 252/70 [51] Int. Cl. F0ln 3/00 [58] Fieldof Search 60/298, 274, 320,

60/200 A, 2 67, 282; l23/4l.l6; 415/114; 416/96; 23/277 C; 252/70 Aug.28, 1973 Attorney-J. L Carpenter, Rob ert Outland et a].

[5 7] ABSTRACT A thermal reactor preferably having in a preferredembodiment, an insulated reaction chamber in which engine exhaust gasesare exothermically reacted to reduce undesirable exhaust emissions. Theinner liner of the reaction chamber is protected against overheatingduring temporary periods of excessive temperature operation bysurrounding the outer surfaces of the liner with a fusible materialhaving a melting point between the normal operating temperature of thereactor and the maximum operating temperature. The latent heat of fusionof the fusible material acts as a heat sink, absorbing heat upon meltingof the material so as to maintain the walls of the inner liner belowtheir maximum operating temperatures during temporary periods ofabnormally high temperature operation due to engine malfunction or thelike.

3 Claims, 2 Drawing Figures Patented Aug. 28, 1973 3,754,398

INVENTOR.

ATTORNEY THERMAL ENGINE EXHAUST REACTOR WITH OVER-TEMPERATURE PROTECTIONBACKGROUND OF THE INVENTION A number of types of what might be termedthermal reactors are in use or are proposed for use in conjunction withthe internal combustion engines of automotive vehicles to cause orencourage exothermic reactions of the exhaust gases in which undesirableconstituents are burned or otherwise removed therefrom. Such thermalreactors include, for example, so-called exhaust reactors involvingenlarged chambers in which combustion takes place, catalytic converterswhich include means for encouraging the reaction of combustibles withthe aid of a catalyst and exhaust reverters involving, for example, thereduction of oxides of nitrogen in a catalyst encouraged reaction.

An operating problem which may be encountered with thermal reactors isthe problem of temporary operation at excessive temperatures with thepossibility of resultant damage to the reactor unit. In engine manifoldreactors, for example, excessively rich carburetion of the engine ora'misfiring cylinder can substantially increase the unburnedhydrocarbons in the engine exhaust which, when burned in the reactor,may increase internal temperatures beyond safe operating limits, re-

sulting in damage to the reactor structure itself and possible failureof the unit. The cost and inconvenience of such failures makes desirablethe provision of means for preventing such over-temperature conditionsor protecting the thermal reactor, of whatever type, against failure dueto such high temperature operation until the cause can be corrected.

SUMMARY OF THE INVENTION The present invention provides means forprotecting the structure of thermal reactors of various types againstdamage due to temporary periods of operation at excessive temperatures.The protection means involves the provision of a fusion material,surrounding the inner liner of the reactor, which melts during hightemperature operation acting as a heat sink to absorb heat from thewalls of the inner liner, thereby protecting the walls against reachingexcessive temperatures.

Various other features and advantages of the invention will be moreapparent from the following description of certain preferredembodiments, taken together with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a diagrammatic cross-sectional view of one embodiment ofexhaust reactor having protection means according to the invention, and

FIG. 2 is a view similar to FIG. 1 but showing an alternative embodimentof exhaust reactor according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 of the drawing,numeral 10 generally indicates, in diagrammatic fashion, a thermalreactor which may be of any suitable type but, in the present instance,is of the type commonly referred to as an exhaust reactor. In suchexhaust reactors, burning of combustibles present in the exhaust gasesof an internal combustion engine in the presence of excess air isencouraged through extended residence time within an insulated chamber.

Reactor 10 includes an inner reaction-chamberdefining liner 12 havingattached thereto a plurality of baffles 14 which together define anextended gas flow path through the reaction chamber. One or more inletconnections I6 are provided which connect the reaction chamber with theexhaust gas outlet ports of an internal combustion engine, not shown. Anair supply tube 18 connects with the inlet connection 16 and with asource of air such as an engine driven air pump to supply excess air formixing with the engine exhaust gases delivered to the exhaust reactorfor combustion therein. An outlet connection 20 at the opposite end ofthe reaction chamber from the inlet connection provides a path for theremoval of treated exhaust gases from the reactor and would normally beconnected with the vehicle muffler or the like.

Surrounding the inner liner 12 of the reactor is an enclosed chamber 22outwardly defined by a housing or intermediate wall 24. A body ofsuitable insulation material 26 surrounds the intermediate wall 24 andis retained in place by an outer shell 28.

The interior of the enclosed chamber 22 is substantially filled with afusible heat-absorbing material 30, such as, for example, magnesiumfluoride or magnesium silicide, the selection of a material beingdependent on the desired normal and maximum operating temperatures ofthe units. The fusible material is arranged to contact the outersurfaces of the inner liner 12. Upon reaching its melting temperature,the material acts as a heat sink, absorbing heat from the inner liner asit melts.

Preferably the fusible material is selected to have a high latent heatof fusion so that it will provide a relatively large heat capacity. Inorder to provide the desired protection for the inner liner, the fusiblematerial must be selected to have a melting temperature which is higherthan that reached during operation of the reactor under normalconditions so that the material will remain solid under such conditions.The melting temperature must, however, be below the temperatures reachedduring operation of the reactor at abnormally high temperatures whichwould otherwise cause damage to the interior walls of the reactorchamber. In this way the melting of the fusible material under hightemperature conditions will draw heat from the walls of the inner linerprotecting it against the damage until all of the fusible material hasbeen melted.

Suitable indicating means may be provided in conjunction with thereactor to warn the vehicle operator of the abnormal operating conditionso that the condition may be corrected before the temporary protectionsupplied by melting of the fusible material is exhausted and permanentdamage to the reactor occurs.

The embodiment of FIG. 2 is identical in most respects to theconstruction of FIG. 1 and, accordingly, primed numerals are utilized toidentify the similar components. The difference in the embodiment ofFIG. 2 is that an expansion space 32 is provided in the enclosed chamber22' above the level of the fusible material 30' in its solid state so asto provide room for expansion of the volume of the fusible material whenit is changed to its liquid state.

Suitable materials for use in thermal reactors of high temperaturestainless steel construction or the like may be, for example, metallicsalts, examples of which are magnesium fluoride which has a meltingtemperature of 2,303 F. and magnesium silicide which has a meltingtemperature of 2,012 F. It is apparent that numerous other fusiblematerials might be appropriate for use to provide the necessary heatsink in a particular reactor design, depending upon the normal andmaximum operating temperatures as previously noted.

While the invention has been described by reference to certain preferredembodiments chosen for purposes of illustration, it is intended that theinvention not be limited except by the language of the following claims.

I claim:

1. For use with an internal combustion engine a thermal reactor devicefor removing undesirable substances from the engine exhaust gases, saidthermal reactor comprising an inner liner defining a high temperaturereaction chamber,

an outer housing, spacedly surrounding said inner liner and defining anenclosed space therebetween, and

a fusible heat absorbing material within said enclosed space andcontacting the outer surfaces of said inner liner that are exposed tosaid space, said heat absorbing material being selected from the groupof metal salts consisting of magnesium fluoride and magnesium silicideand having a melting temperature which is greater than the normaloperating temperature of the inner liner surfaces it contacts and whichis below the desired maximum operating temperatures of said surfaceswhereby, during operation of said thermal reactor at excessive reactiontemperatures, said inner liner wall is maintained below its maximumoperating temperature by melting of said fusible material.

2. The reactor of claim 1 wherein said enclosed space between said innerliner and outer housing includes an expansion volume above the level ofsaid inner liner to provide for expansion of said fusible material dueto a change of state.

3. The reactor of claim 1 and further comprising heat insulating meanssurrounding said outer housing and adapted to prevent excessive heatflow therefrom.

1. For use with an internal combustion engine a thermal reactor devicefor removing undesirable substances from the engine exhaust gases, saidthermal reactor comprising an inner liner defining a high temperaturereaction chamber, an outer housing, spacedly surrounding said innerliner and defining an enclosed space therebetween, and a fusible heatabsorbing material within said enclosed space and contacting the outersurfaces of said inner liner that are exposed to said space, said heatabsorbing material being selected from the group of metal saltsconsisting of magnesium fluoride and magnesium silicide and having amelting temperature which is greater than the normal operatingtemperature of the inner liner surfaces it contacts and which is belowthe desired maximum operating temperatures of said surfaces whereby,during operation of said thermal reactor at excessive reactiontemperatures, said inner liner wall is maintained below its maximumoperating temperature by melting of said fusible material.
 2. Thereactor of claim 1 wherein said enclosed space between said inner linerand outer housing includes an expansion volume above the level of saidinner liner to provide for expansion of said fusible material due to achange of state.
 3. The reactor of claim 1 and further comprising heatinsulating means surrounding said outer housing and adapted to preventexcessive heat flow therefrom.